BU researcher discovers binary asteroid

Michael Shepard, professor of geography and geosciences, discovered a binary asteroid April 10 while working at the Arecibo Observatory radio telescope in Puerto Rico. While observing asteroid 2005NB7, which was 16 lunar distances (about 3.8 million miles) from Earth, Shepard saw the asteroid had a smaller partner. Shepard previously discovered a binary asteroid while working at Arecibo in 2004 with a BU student.

"Until 10 years ago, it was very rare to discover a binary asteroid," said Shepard. "Now, we find that about one in six asteroids is a binary."

The larger partner in the binary pair is about 500 meters in diameter; the smaller partner has a diameter of 200 to 300 meters. "The two bodies mutually orbit one another and the gravitational pull is very weak," said Shepard. "If you were standing on one of them, you could toss a pebble and put it into orbit."

The radio telescope at Arecibo has unique qualities that make it particularly useful for studying asteroids, according to Shepard. Built into a natural depression that has been enlarged, the telescope consists of a reflective dish of perforated aluminum panels that is 1,000 feet in diameter and 167 feet deep.

"The telescope can tell the speed of an object within millimeters per second and track its position to within meters," said Shepard. Several years ago, the Arecibo telescope was used to determine that an asteroid that was feared to be on a collision course with the Earth would, in-fact, miss the planet.

Shepard will next create three-dimensional computer models of the asteroid. Radar data from Arecibo will be input into a networked cluster of computers at BU, referred to as a "Beowulf" cluster. The computers will analyze the data using an application called "Shape" that creates the three dimensional renderings.